scispace - formally typeset
Search or ask a question

Showing papers on "Ecosystem published in 2000"


Journal ArticleDOI
10 Mar 2000-Science
TL;DR: This study identified a ranking of the importance of drivers of change, aranking of the biomes with respect to expected changes, and the major sources of uncertainties in projections of future biodiversity change.
Abstract: Scenarios of changes in biodiversity for the year 2100 can now be developed based on scenarios of changes in atmospheric carbon dioxide, climate, vegetation, and land use and the known sensitivity of biodiversity to these changes. This study identified a ranking of the importance of drivers of change, a ranking of the biomes with respect to expected changes, and the major sources of uncertainties. For terrestrial ecosystems, land-use change probably will have the largest effect, followed by climate change, nitrogen deposition, biotic exchange, and elevated carbon dioxide concentration. For freshwater ecosystems, biotic exchange is much more important. Mediterranean climate and grassland ecosystems likely will experience the greatest proportional change in biodiversity because of the substantial influence of all drivers of biodiversity change. Northern temperate ecosystems are estimated to experience the least biodiversity change because major land-use change has already occurred. Plausible changes in biodiversity in other biomes depend on interactions among the causes of biodiversity change. These interactions represent one of the largest uncertainties in projections of future biodiversity change.

8,401 citations


Journal ArticleDOI
20 Apr 2000-Nature
TL;DR: Data of net ecosystem carbon exchange, collected between 1996 and 1998 from 15 European forests, confirm that many European forest ecosystems act as carbon sinks and indicate that, in general, ecosystem respiration determines netcosystem carbon exchange.
Abstract: Carbon exchange between the terrestrial biosphere and the atmosphere is one of the key processes that need to be assessed in the context of the Kyoto Protocol1. Several studies suggest that the terrestrial biosphere is gaining carbon2,3,4,5,6,7,8, but these estimates are obtained primarily by indirect methods, and the factors that control terrestrial carbon exchange, its magnitude and primary locations, are under debate. Here we present data of net ecosystem carbon exchange, collected between 1996 and 1998 from 15 European forests, which confirm that many European forest ecosystems act as carbon sinks. The annual carbon balances range from an uptake of 6.6 tonnes of carbon per hectare per year to a release of nearly 1 t C ha-1 yr-1, with a large variability between forests. The data show a significant increase of carbon uptake with decreasing latitude, whereas the gross primary production seems to be largely independent of latitude. Our observations indicate that, in general, ecosystem respiration determines net ecosystem carbon exchange. Also, for an accurate assessment of the carbon balance in a particular forest ecosystem, remote sensing of the normalized difference vegetation index or estimates based on forest inventories may not be sufficient.

1,636 citations


Journal ArticleDOI
TL;DR: A conference entitled "Soil Health: Managing the Biological Component of Soil Quality" was held in the USA in 1998 to help increase awareness of the importance and utility of soil organisms as indicators of soil quality and determinants of soil health.

1,462 citations


Journal ArticleDOI
30 Nov 2000-Nature
TL;DR: In both lakes and terrestrial systems, herbivores should have low growth efficiencies when consuming autotrophs with typical carbon-to-nutrient ratios and stoichiometric constraints on herbivore growth appear to be qualitatively similar and widespread in both environments.
Abstract: Biological and environmental contrasts between aquatic and terrestrial systems have hindered analyses of community and ecosystem structure across Earth's diverse habitats. Ecological stoichiometry1,2 provides an integrative approach for such analyses, as all organisms are composed of the same major elements (C, N, P) whose balance affects production, nutrient cycling, and food-web dynamics3,4. Here we show both similarities and differences in the C:N:P ratios of primary producers (autotrophs) and invertebrate primary consumers (herbivores) across habitats. Terrestrial food webs are built on an extremely nutrient-poor autotroph base with C:P and C:N ratios higher than in lake particulate matter, although the N:P ratios are nearly identical. Terrestrial herbivores (insects) and their freshwater counterparts (zooplankton) are nutrient-rich and indistinguishable in C:N:P stoichiometry. In both lakes and terrestrial systems, herbivores should have low growth efficiencies (10–30%) when consuming autotrophs with typical carbon-to-nutrient ratios. These stoichiometric constraints on herbivore growth appear to be qualitatively similar and widespread in both environments.

1,335 citations


Journal ArticleDOI
TL;DR: The significance of polyphenols for nutrient cycling and plant productivity is still uncertain, but it could provide an alternative or complementary explanation for the variability in polyphenol production by plants.
Abstract: Interspecific variation in polyphenol production by plants has been interpreted in terms of defense against herbivores. Several recent lines of evidence suggest that polyphenols also influence the pools and fluxes of inorganic and organic soil nutrients. Such effects could have far-ranging consequences for nutrient competition among and between plants and microbes, and for ecosystem nutrient cycling and retention. The significance of polyphenols for nutrient cycling and plant productivity is still uncertain, but it could provide an alternative or complementary explanation for the variability in polyphenol production by plants.

1,051 citations


Journal ArticleDOI
01 Sep 2000-Ecology
TL;DR: It is found that extracellular enzyme responses of a forest-floor microbial community to chronically applied aqueous NH4NO3 can explain both increased and decreased litter decomposition rates caused by added N.
Abstract: Some natural ecosystems near industrialized and agricultural areas receive atmospheric nitrogen inputs that are an order of magnitude greater than those presumed for preindustrial times. Because nitrogen (N) often limits microbial growth on dead vegetation, increased N input can be expected to affect the ecosystem process of decomposition. We found that extracellular enzyme responses of a forest-floor microbial community to chronically applied aqueous NH4NO3 can explain both increased and decreased litter decomposition rates caused by added N. Microbes responded to N by increasing cellulase activity in decaying leaf litter of flowering dogwood, red maple, and red oak, but in high-lignin oak litter, the activity of lignin-degrading phenol oxidase declined substantially. We believe this is the first report of reduced ligninolytic enzyme activity caused by chronic N addition in an ecosystem. This result provides evidence that ligninolytic enzyme suppression can be an important mechanism explaining decreased ...

943 citations


Journal ArticleDOI
01 Oct 2000-Oikos
TL;DR: Recent theoretical developments in the area of biodiversity and ecosystem functioning suggest that linking community and ecosystem ecology is a fruitful avenue, which paves the way for a new ecological synthesis.
Abstract: The relationship between biodiversity and ecosystem functioning has emerged as a major scientific issue today. As experiments progress, there is a growing need for adequate theories and models to provide robust interpretations and generalisations of experimental results, and to formulate new hypotheses. This paper provides an overview of recent theoretical advances that have been made on the two major questions in this area: (1) How does biodiversity affect the magnitude of ecosystem processes (short-term effects of biodiversity)? (2) How does biodiversity contribute to the stability and maintenance of ecosystem processes in the face of perturbations (long-term effects of biodiversity)? Positive short-term effects of species diversity on ecosystem processes, such as primary productivity and nutrient retention, have been explained by two major types of mechanisms: (1) functional niche complementarity (the complementarity effect), and (2) selection of extreme trait values (the selection effect). In both cases, biodiversity provides a range of phenotypic trait variation. In the complementarity effect, trait variation then forms the basis for a permanent association of species that enhances collective performance. In the selection effect, trait variation comes into play only as an initial condition, and a selective process then promotes dominance by species with extreme trait values. Major differences between within-site effects of biodiversity and across-site productivity–diversity patterns have also been clarified. The local effects of diversity on ecosystem processes are expected to be masked by the effects of varying environmental parameters in across-site comparisons. A major reappraisal of the paradigm that has dominated during the last decades seems necessary if we are to account for long-term effects of biodiversity on ecosystem functioning. The classical deterministic, equilibrium approaches to stability do not explain the reduced temporal variability of aggregate ecosystem properties that has been observed in more diverse systems. On the other hand, stochastic, nonequilibrium approaches do show two types of biodiversity effects on ecosystem productivity in a fluctuating environment: (1) a buffering effect, i.e., a reduction in the temporal variance; and (2) a performance-enhancing effect, i.e., an increase in the temporal mean. The basic mechanisms involved in these long-term insurance effects are very similar to those that operate in short-term biodiversity effects: temporal niche complementarity, and selection of extreme trait values. The ability of species diversity to provide an insurance against environmental fluctuations and a reservoir of variation allowing adaptation to changing conditions may be critical in a long-term perspective. These recent theoretical developments in the area of biodiversity and ecosystem functioning suggest that linking community and ecosystem ecology is a fruitful avenue, which paves the way for a new ecological synthesis.

912 citations


Journal ArticleDOI
TL;DR: In this article, the effects of human impact on biodiversity of European forests in the light of recent views on disturbances and succession in ecosystems, and discuss recent ideas on how biodiversity affects ecosystem functions such as productivity and ecosystem stability.

790 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present documented input parameters for a process-based ecosystem simulation model, BIOME-BGC, for major natural temperate biomes, including turnover and mortality, allocation, carbon to nitrogen ratios (C:N), the percent of plant material in labile, cellulose, and lignin pools, leaf morphology, leaf conductance rates and limitations, canopy water interception and light extinction.
Abstract: Ecosystem simulation models use descriptive input parameters to establish the physiology, biochemistry, structure, and allocation patterns of vegetation functional types, or biomes. For single-stand simulations it is possible to measure required data, but as spatial resolution increases, so too does data unavailability. Generalized biome parameterizations are then required. Undocumented parameter selection and unknown model sensitivity to parameter variation for larger-resolution simulations are currently the major limitations to global and regional modeling. The authors present documented input parameters for a process-based ecosystem simulation model, BIOME–BGC, for major natural temperate biomes. Parameter groups include the following: turnover and mortality; allocation; carbon to nitrogen ratios (C:N); the percent of plant material in labile, cellulose, and lignin pools; leaf morphology; leaf conductance rates and limitations; canopy water interception and light extinction; and the percent of...

789 citations


Journal ArticleDOI
TL;DR: This work identifies 32 syndromes of biotic disturbance in North American forests that should be carefully evaluated for their responses to climate change and suggests a list of research priorities that will allow us to refine these risk assessments and adopt forest management strategies that anticipate changes inBiotic disturbance regimes and mitigate the ecological, social, and economic risks.

778 citations


Journal ArticleDOI
TL;DR: In this article, carbon isotope ratios (δ13C) in soil organic matter (SOM) and soil respired CO2 provide insights into dynamics of the carbon cycle.
Abstract: Analyses of carbon isotope ratios (δ13C) in soil organic matter (SOM) and soil respired CO2 provide insights into dynamics of the carbon cycle. δ13C analyses do not provide direct measures of soil CO2 efflux rates but are useful as a constraint in carbon cycle models. In many cases, δ13C analyses allow the identification of components of soil CO2 efflux as well as the relative contribution of soil to overall ecosystem CO2 fluxes. δ13C values provide a unique tool for quantifying historical shifts between C3 and C4 ecosystems over decadal to millennial time scales, which are relevant to climate change and land-use change issues. We identify the need to distinguish between δ13C analyses of SOM and those of soil CO2 efflux in carbon cycle studies, because time lags in the turnover rates of different soil carbon components can result in fluxes and stocks that differ in isotopic composition (disequilibrium effect). We suggest that the frequently observed progressive δ13C enrichment of SOM may be related to a g...

Journal ArticleDOI
TL;DR: Little support is found for the hypothesis that there is a strong dependence of ecosystem function on the full complement of diversity within sites, and the conservation community should take a cautious view of endorsing this linkage as a model to promote conservation goals.
Abstract: We evaluate the empirical and theoretical support for the hypothesis that a large proportion of native species richness is required to maximize ecosystem stability and sustain function. This assessment is important for conservation strategies because sustenance of ecosystem functions has been used as an argument for the conservation of species. If ecosystem functions are sustained at relatively low species richness, then arguing for the conservation of ecosystem function, no matter how important in its own right, does not strongly argue for the conservation of species. Additionally, for this to be a strong conservation argument the link between species diversity and ecosystem functions of value to the human community must be clear. We review the empirical literature to quantify the support for two hypotheses: (1) species richness is positively correlated with ecosystem function, and (2) ecosystem functions do not saturate at low species richness relative to the observed or experimental diversity. Few empirical studies demonstrate improved function at high levels of species richness. Second, we analyze recent theoretical models in order to estimate the level of species richness required to maintain ecosystem function. Again we find that, within a single trophic level, most mathematical models predict saturation of ecosystem function at a low proportion of local species richness. We also analyze a theoretical model linking species number to ecosystem stability. This model predicts that species richness beyond the first few species does not typically increase ecosystem stability. One reason that high species richness may not contribute significantly to function or stability is that most communities are characterized by strong dominance such that a few species provide the vast majority of the community biomass. Rapid turnover of species may rescue the concept that diversity leads to maximum function and stability. The role of turnover in ecosystem function and stability has not been investigated. Despite the recent rush to embrace the linkage between biodiversity and ecosystem function, we find little support for the hypothesis that there is a strong dependence of ecosystem function on the full complement of diversity within sites. Given this observation, the conservation community should take a cautious view of endorsing this linkage as a model to promote conservation goals.

Journal ArticleDOI
06 Jan 2000-Nature
TL;DR: It is shown here that low transfer efficiencies between primary producers and consumers during cyanobacteria bloom conditions are related to low relative eicosapentaenoic acid (20:5ω3) content of the primary producer community, indicating that limitation of zooplankton production by this essential fatty acid is of central importance at the pelagic producer–consumer interface.
Abstract: The factors that regulate energy transfer between primary producers and consumers in aquatic ecosystems have been investigated for more than 50 years. Among all levels of the food web (plants, herbivores, carnivores), the plant-animal interface is the most variable and least predictable link. In hypereutrophic lakes, for example, biomass and energy transfer is often inhibited at the phytoplankton-zooplankton link, resulting in an accumulation of phytoplankton biomass instead of sustaining production at higher trophic levels, such as fish. Accumulation of phytoplankton (especially cyanobacteria) results in severe deterioration of water quality, with detrimental effects on the health of humans and domestic animals, and diminished recreational value of water bodies. We show here that low transfer efficiencies between primary producers and consumers during cyanobacteria bloom conditions are related to low relative eicosapentaenoic acid (20:5omega3) content of the primary producer community. Zooplankton growth and egg production were strongly related to the primary producer 20:5omega3 to carbon ratio. This indicates that limitation of zooplankton production by this essential fatty acid is of central importance at the pelagic producer-consumer interface.

Journal ArticleDOI
29 Jun 2000-Nature
TL;DR: It is found that food-chain length increases with ecosystem size, but that the length of the food chain is not related to productivity, which supports the hypothesis thatcosystem size, and not resource availability, determines food- chain length in natural ecosystems.
Abstract: Food-chain length is an important characteristic of ecological communities: it influences community structure, ecosystem functions and contaminant concentrations in top predators. Since Elton first noted that food-chain length was variable among natural systems, ecologists have considered many explanatory hypotheses, but few are supported by empirical evidence. Here we test three hypotheses that predict food-chain length to be determined by productivity alone (productivity hypothesis), ecosystem size alone (ecosystem-size hypothesis) or a combination of productivity and ecosystem size (productive-space hypothesis). The productivity and productive-space hypotheses propose that food-chain length should increase with increasing resource availability; however, the productivity hypothesis does not include ecosystem size as a determinant of resource availability. The ecosystem-size hypothesis is based on the relationship between ecosystem size and species diversity, habitat availability and habitat heterogeneity. We find that food-chain length increases with ecosystem size, but that the length of the food chain is not related to productivity. Our results support the hypothesis that ecosystem size, and not resource availability, determines food-chain length in these natural ecosystems.

Journal ArticleDOI
01 Aug 2000-Oikos
TL;DR: Although fumigation reduced soil microbial biodiversity, there was evidence to suggest that it selected for organisms with particular physiological characteristics, and specific functional parameters may be a more sensitive indicator of environmental change than general parameters.
Abstract: A technique based on progressive fumigation was used to reduce soil microbial biodiversity, and the effects of such reductions upon the stability of key soil processes were measured. Mineral soil samples from a grassland were fumigated with chloroform for up to 24 h and then incubated for 5 months to allow recolonisation by surviving organisms. The diversity of cultivable and non-cultivable bacteria, protozoa and nematodes was progressively reduced by increasing fumigation times, as was the number of trophic groups, phyla within trophic groups, and taxa within phyla. Total microbial biomass was similar within fumigated soils, but lower than for unfumigated soil. There was no direct relationship between biodiversity and function. Some broad-scale functional parameters increased as biodiversity decreased, e.g. thymidine incorporation, growth on added nutrients, and the decomposition rate of plant residues. Other more specific parameters decreased as biodiversity decreased, e.g. nitrification, denitrification and methane oxidation. Thus specific functional parameters may be a more sensitive indicator of environmental change than general parameters. Although fumigation reduced soil microbial biodiversity, there was evidence to suggest that it selected for organisms with particular physiological characteristics. The consequences of this for interpreting biodiversity – function relationships are discussed. The stability of the resulting communities to perturbation was further examined by imposing a transient (brief heating to 40°C) or a persistent (addition of CuSO4) stress. Decomposition of grass residues was determined on three occasions after such perturbations. The soils clearly demonstrated resilience to the transient stress; decomposition rates were initially depressed by the stress and recovered over time. Resilience was reduced in the soils with decreasing biodiversity. Soils were not resilient to the persistent stress, there was no recovery in decomposition rate over time, but the soils with the highest biodiversity were more resistant to the stress than soils with impaired biodiversity. The study of functional stability under applied perturbation is a powerful means of examining the effects of biodiversity.

Journal ArticleDOI
02 Nov 2000-Nature
TL;DR: Using free-air CO2 enrichment (FACE) technology in an intact Mojave Desert ecosystem, it is shown that new shoot production of a dominant perennial shrub is doubled by a 50% increase in atmospheric CO2 concentration in a high rainfall year, but elevated CO 2 does not enhance production in a drought year.
Abstract: Arid ecosystems, which occupy about 20% of the earth's terrestrial surface area, have been predicted to be one of the most responsive ecosystem types to elevated atmospheric CO2 and associated global climate change1,2,3. Here we show, using free-air CO2 enrichment (FACE) technology in an intact Mojave Desert ecosystem4, that new shoot production of a dominant perennial shrub is doubled by a 50% increase in atmospheric CO2 concentration in a high rainfall year. However, elevated CO2 does not enhance production in a drought year. We also found that above-ground production and seed rain of an invasive annual grass increases more at elevated CO2 than in several species of native annuals. Consequently, elevated CO2 might enhance the long-term success and dominance of exotic annual grasses in the region. This shift in species composition in favour of exotic annual grasses, driven by global change, has the potential to accelerate the fire cycle, reduce biodiversity and alter ecosystem function in the deserts of western North America.


ReportDOI
01 Jan 2000
TL;DR: Brown et al. as discussed by the authors reviewed the effects of fire on flora and fuels and provided a state-of-the-art review about the ecological role of fire in ecosystems, including fire regime classification, autecological effects, fire regime characteristics and postfire plant community development.
Abstract: ____________________________________ Brown, James K.; Smith, Jane Kapler, eds. 2000. Wildland fire in ecosystems: effects of fire on flora. Gen. Tech. Rep. RMRS-GTR-42-vol. 2. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 257 p. This state-of-knowledge review about the effects of fire on flora and fuels can assist land managers with ecosystem and fire management planning and in their efforts to inform others about the ecological role of fire. Chapter topics include fire regime classification, autecological effects of fire, fire regime characteristics and postfire plant community developments in ecosystems throughout the United States and Canada, global climate change, ecological principles of fire regimes, and practical considerations for managing fire in an ecosytem context.

Book
01 Jan 2000
TL;DR: The third edition of "Insect Ecology: An Ecosystem Approach" provides a modern perspective of insect ecology that integrates two approaches traditionally used to study insect ecology: evolutionary and ecosystem.
Abstract: 1 Overview 2 Responses to Abiotic Conditions 3 Resource Acquisition 4 Resource Allocation 5 Population Systems 6 Population Dynamics 7 Biogeography 8 Species Interactions 9 Community Structure 10 Community Dynamics 11 Ecosystem Structure and Function 12 Herbivory 13 Pollination, Seed Predation and Seed Dispersal 14 Decomposition and Pedogenesis 15 Insects as Regulators of Ecosystem Processes 16 Synthesis

Journal ArticleDOI
17 Mar 2000-Science
TL;DR: The effects of increasing carbon dioxide (CO2) and climate on net carbon storage in terrestrial ecosystems of the conterminous United States for the period 1895-1993 were modeled with new, detailed historical climate information, suggesting that processes such as regrowth on abandoned agricultural land or in forests harvested before 1980 have effects as large as or larger than the direct effects of CO2 and climate.
Abstract: The effects of increasing carbon dioxide (CO2) and climate on net carbon storage in terrestrial ecosystems of the conterminous United States for the period 1895-1993 were modeled with new, detailed historical climate information. For the period 1980-1993, results from an ensemble of three models agree within 25%, simulating a land carbon sink from CO2 and climate effects of 0.08 gigaton of carbon per year. The best estimates of the total sink from inventory data are about three times larger, suggesting that processes such as regrowth on abandoned agricultural land or in forests harvested before 1980 have effects as large as or larger than the direct effects of CO2 and climate. The modeled sink varies by about 100% from year to year as a result of climate variability.

Journal ArticleDOI
TL;DR: In this paper, the amplitude of a response and time to return to the current state before application of stress could serve as measures of soil health, and the occurrence of epiphytotics forms an indication of an ecosystem in distress.

BookDOI
01 Jan 2000
TL;DR: In this paper, the authors studied the carbon and nitrogen cycle of forest ecosystems in the European Transect and found that the carbon cycle is linked with plant nutrition and ecosystem processes.
Abstract: A Introduction to the European Transect.- 1 The Carbon and Nitrogen Cycle of Forest Ecosystems.- 1.1 Introduction.- 1.2 The Carbon and Nitrogen Cycles.- 1.3 The NIPHYS/CANIF Project.- 1.4 Experimental Design.- 1.5 Conclusions.- References.- 2 Experimental Sites in the NIPHYS/CANIF Project.- 2.1 Site Description. The NIPHYS/CANIF Transect.- 2.2 Soil Characteristics.- 2.3 Ecosystem C and N Pools.- 2.4 Database.- 2.5 Conclusions.- References.- B Plant-Related Processes.- 3 Tree Biomass, Growth and Nutrient Pools.- 3.1 Introduction.- 3.2 Experimental Background.- 3.3 Biomass.- 3.4 Forest Productivity.- 3.5 Carbon and Nutrient Pools.- 3.6 Allometric and Functional Relations.- 3.7 Conclusion.- References.- 4 Linking Plant Nutrition and Ecosystem Processes.- 4.1 Introduction.- 4.2 Experimental Approach.- 4.3 Nutrient Concentrations.- 4.4 Nutrient Contents.- 4.5 Nitrogen Partitioning in Different Tree Compartments.- 4.6 Ecosystem C and N Pools.- 4.7 Conclusions.- References.- 5 Root Growth and Response to Nitrogen.- 5.1 Introduction.- 5.2 Approaches to the Study of Root Growth.- 5.3 Root Growth Measurements Obtained by Soil Coring.- 5.4 Root Growth Measurements Obtained by Root Windows.- 5.5 Root Growth Measurements Obtained by In-Growth Cores.- 5.6 Root Growth at Different European Forest Sites.- 5.7 Conclusion.- References.- 6 Nitrogen Uptake Processes in Roots and Mycorrhizas.- 6.1 Introduction.- 6.2 Approaches to Study Different Aspects of the N Uptake Process.- 6.3 Studies with Excised Roots and Mycorrhizas.- 6.4 Field-Based Experiments.- 6.5 Conclusions.- References.- 7 The Fate of 15N-Labelled Nitrogen Inputs to Coniferous and Broadleaf Forests.- 7.1 Introduction.- 7.2 Sites of Investigation.- 7.3 Approaches to Study the Fate of 15N-Labelled Nitrogen Inputs.- 7.4 N Release and Tree Uptake from 15N-Labelled Decomposing Litter in a Beech Forest in Aubure.- 7.5 Ecosystem Partitioning of 15N-Labelled Ammonium and Nitrate on the Sites in the Fichtelgebirge and Steigerwald.- 7.6 Conclusion.- References.- 8 Canopy Uptake and Utilization of Atmospheric Pollutant Nitrogen.- 8.1 Introduction.- 8.2 Atmospheric Nitrogen Pollutants.- 8.3 Pathways for Canopy Uptake of Nitrogen.- 8.4 Approaches to the Determination of Canopy Uptake of Nitrogen.- 8.5 Review of Research.- 8.6 Role in the Critical Load.- 8.7 Ecophysiological Consequences of Canopy N Uptake.- 8.8 Conclusions.- 8.9 Way Forward.- 8.10 Policy Implications.- References.- 9 Biotic and Abiotic Controls Over Ecosystem Cycling of Stable Natural Nitrogen, Carbon and Sulphur Isotopes.- 9.1 Introduction.- 9.2 Approaches to the Study of Stable Isotopes in the Field.- 9.3 ?15N of Ammonium and Nitrate in Wet Deposition.- 9.4 Stable Isotope Signatures in Different Ecosystem Compartments.- 9.5 ?15N Signatures as Indicators of N Saturation in Forest Ecosystems.- 9.6 Conclusion.- References.- C Heterotrophic Processes.- 10 Soil Respiration in Beech and Spruce Forests in Europe: Trends, Controlling Factors, Annual Budgets and Implications for the Ecosystem Carbon Balance.- 10.1 Introduction.- 10.2 Approaches to Measuring Soil Respiration.- 10.3 Daily and Seasonal Trends in Soil Respiration and Climatic Variables.- 10.4 Factors Controlling Soil Respiration.- 10.5 Comparison of Chamber Measurements with the Eddy Covariance Measurements Below the Canopy.- 10.6 Annual Budgets of Soil Respiration.- 10.7 Conclusion.- References.- 11 Annual Carbon and Nitrogen Fluxes in Soils Along the European Forest Transect, Determined Using the 14C-Bomb.- 11.1 Introduction.- 11.2 Forests, Sampling Procedure and Analysis.- 11.3 Model Description.- 11.4 Estimations of C and N Pools and Fluxes.- 11.5 Pools and Distribution of Carbon and Nitrogen in Soil Profiles.- 11.6 Variations in the Carbon Age and Mean Residence Times (MRTs).- 11.7 Annual Carbon and Nitrogen Fluxes.- 11.8 General Discussion.- 11.9 Conclusion.- References.- 12 Carbon Mineralisation in European Forest Soils.- 12.1 Introduction.- 12.2 Experimental Background.- 12.3 C Mineralisation in the North-South Transect.- 12.4 Long-Term Fertilisation Experiments.- 12.5 Mean Residence Time.- 12.6 Comparison of Intact and Sieved Soil Cores.- 12.7 Conclusion.- References.- 13 Litter Decomposition.- 13.1 Introduction.- 13.2 Factors Affecting the Decomposition Process.- 13.3 Enzymatic Activity.- 13.4 Nitrogen Dynamics in Decomposing Litter.- 13.5 Decomposition Studies in Europe: from DECO, VAMOS, MICS to CANIF.- 13.6 Decomposition Studies Within a Latitudinal Transect of European Beech Forests.- 13.7 Conclusion.- References.- 14 Soil Nitrogen Turnover - Mineralisation, Nitrification and Denitrification in European Forest Soils.- 14.1 Background and Aim of the Study.- 14.2 Methods Used to Study N Turnover.- 14.3 Net N Mineralisation Based on Laboratory Studies.- 14.4 Net Nitrification Based on Laboratory Studies.- 14.5 Manipulation of pH, N Availability and Nitrifier Density in the Laboratory.- 14.6 Autotrophic Versus Heterotrophic Nitrification.- 14.7 Net N Mineralisation and Nitrification in N-Fertilisation Experiments.- 14.8 Comparison of N Turnover in Similar Soils at Different Climate.- 14.9 Comparison of N Turnover in Sieved and Intact Soil Cores.- 14.10 In Situ Mineralisation Studies at Aubure.- 14.11 Comparison of in Situ and Laboratory-Based Mineralisation Studies.- 14.12 Denitrification.- 14.13 Final Discussion.- 14.14 Conclusions.- References.- 15 Nitrogen and Carbon Interactions of Forest Soil Water.- 15.1 Introduction.- 15.2 Approaches to Studying the Forest Soil Waters.- 15.3 Soil Water Concentrations of Nitrogen and Carbon.- 15.4 Correlation Between Dissolved Organic Nitrogen and Carbon.- 15.5 Conclusions.- References.- D Diversity-Related Processes.- 16 Fungal Diversity in Ectomyccorhizal Communities of Norway Spruce [Picea abies (L.) Karst.] and Beech (Fagus sylvatica L.) Along North-South Transects in Europe.- 16.1 Introduction.- 16.2 Analysis of Ectomycorrhizal Community Structure and Diversity.- 16.3 ECM Communities of Spruce Forests.- 16.4 ECM Communities of Beech Forests.- 16.5 Genetic Diversity Within a Population of Laccarina amethystina.- 16.6 Isolation and Growth of ECM Fungal Isolates on an Organic N Source.- 16.7 Comparative Evaluation of Ectomycorrhizal Diversity.- 16.8 Conclusion.- References.- 17 Diversity and Role of the Decomposer Food Web.- 17.1 Introduction.- 17.2 Approaches to Investigating Decomposer Communities.- 17.3 The Microflora.- 17.4 The Soil Fauna.- 17.5 Contribution of the Decomposer Food Web to C and N Flows.- 17.6 Conclusions.- References.- 18 Diversity and Role of Microorganisms.- 18.1 Introduction and Background.- 18.2 Experimental Background.- 18.3 Community of Microfungi in Beech Forests.- 18.4 Functional Diversity of Bacteria in the Litter of Coniferous Forests.- 18.5 Conclusion.- References.- E Integration.- 19 Spatial Variability and Long-Term Trends in Mass Balance of Nand S in Central European Forested Catchments.- 19.1 Introduction.- 19.2 Approaches to Studying Long-Term Changes in Watersheds.- 19.3 Temporal Variations and Trends.- 19.4 Budgets.- 19.5 Biological Cycling of Sulphur.- 19.6 Conclusion.- References.- 20 Model Analysis of Carbon and Nitrogen Cycling in Picea and Fagus Forests.- 20.1 Introduction.- 20.2 Model Description.- 20.3 Input Data and Parameter Values.- 20.4 Model Calibration and Comparison with Measured Data.- 20.5 Model Analysis.- 20.6 Conclusions.- References.- 21 Interactions Between the Carbon and Nitrogen Cycle and the Role of Biodiversity: A Synopsis of a Study Along a North-South Transect Through Europe.- 21.1 Introduction.- 21.2 Change of Ecosystem Processes Along the European Transect.- 21.3 What Limits the C and N Fluxes in These Forest Ecosystems?.- 21.4 What Are Net Ecosystem Productivity (NEP) and Net Biome Productivity (NBP) and How Do They Relate to Ecosystem Parameters?.- 21.5 Are There Thresholds and Non-Linearities?.- 21.6 What Role Does Biodiversity Play in Ecosystem Processes?.- 21.7 Conclusions.- References.- Species Index.

Book ChapterDOI
01 Jan 2000
TL;DR: In this article, a range of abundance and biomass of termites in major ecosystems and biogeographical regions is discussed, and representative data are tabulated; transect methods are recommended for biodiversity surveys as they are efficient and have acceptable accuracy.
Abstract: Termite assemblages are considered as complex systems containing species with several modes of feeding and nesting, which have a major though not necessarily dominant role in decomposition and C mineralization processes, and which influence soil properties and structure. Sampling methods for species richness, abundance and biomass and the estimation of food consumption rates are reviewed; transect methods are recommended for biodiversity surveys as they are efficient and have acceptable accuracy. Biases introduced by sampling methods which focus on mounds only and by consumption assays based on baits lead to underestimates of assemblage diversity, abundance and ecological impact. The range of abundance and biomass of termites in major ecosystems and biogeographical regions is discussed and representative data are tabulated. In savanna systems, the turnover of organic matter by termites is roughly comparable to that of mammalian herbivores and bush fires, and as much as 20% of C mineralization may be directly attributed to termites. In forests, absolute C fluxes through populations are generally larger, owing to higher termite biomass, but the relative contribution to C turnover is less. Functional group heterogeneity rather than species richness per se is considered the key link between termite biodiversity and ecosystem functions.

Journal ArticleDOI
01 May 2000-Ecology
TL;DR: In this article, the effect of denitrifier community composition on nitrous oxide (N20) production was evaluated by comparing two geomorphically similar soils from fields in southwest Michigan that differed in plant community composition and disturbance regime: a con-ventionally tilled agricultural field and a never-tilled successional field.
Abstract: We tested the hypothesis that soil microbial diversity affects ecosystem func- tion by evaluating the effect of denitrifier community composition on nitrous oxide (N20) production. Denitrification is a major source of atmospheric N20, an important greenhouse gas and a natural catalyst of stratospheric ozone decay. The major environmental controls on denitrification rate and the mole ratio of N20 produced during denitrification have been incorporated into mechanistic models, but these models are, in general, poor predictors of in situ N20 flux rates. We sampled two geomorphically similar soils from fields in southwest Michigan that differed in plant community composition and disturbance regime: a con- ventionally tilled agricultural field and a never-tilled successional field. We tested whether denitrifier community composition influences denitrification rate and the relative rate of N20 production (AN20/A(N20 + N2)), or rN20, using a soil enzyme assay designed to evaluate the effect of oxygen concentration and pH on the activity of denitrification enzymes responsible for the production and consumption of N20. By controlling, or providing in nonlimiting amounts, all known environmental regulators of denitrifier N20 production and consumption, we created conditions in which the only variable contributing to differences in denitrification rate and rN2O in the two soils was denitrifier community composition. We found that both denitrification rate and rN2O differed for the two soils under controlled incubation conditions. Oxygen inhibited the activity of enzymes involved in N20 production (nitrate reductase, Nar; nitrite reductase, Nir; and nitric oxide reductase, Nor) to a greater extent in the denitrifying community from the agricultural field than in the community from the successional field. The Nar, Nir, and Nor enzymes of the denitrifying community from the successional field, on the other hand, were more sensitive to pH than were those in the denitrifying community from the agricultural field. Moreover, the denitrifying community in the soil from the successional field had relatively more active nitrous oxide reductase (Nos) enzymes, which reduce N20 to N2, than the denitrifying community in the agricultural field. Also, the shape of the rN20 curve with increasing oxygen was different for each denitrifying community. Each of these differences suggests that the denitrifying commu- nities in these two soils are different and that they do not respond to environmental regulators in the same manner. We thus conclude that native microbial community composition reg- ulates an important ecosystem function in these soils.

Book
01 Jan 2000
TL;DR: This chapter discusses the effects of climate change on the evolution and distribution of species, and the results of evolution: convergent and parallel evolution.
Abstract: Chapter 1: Ecology and How to Do It 1.1 Introduction 1.2 Scales, diversity and rigor 1.2.1 Questions of scale 1.2.2 The diversity of ecological evidence 1.2.3 Statistics and scientific rigor 1.3 Ecology in practice 1.3.1 The brown trout in New Zealand - effects on individuals, populations, communities and ecosystems 1.3.2 Successions on old fields in Minnesota - a study in time and space 1.3.3 Hubbard Brook - a long-term commitment of large-scale significance 1.3.4 A model study: Genetically modified crops - bad for biodiversity? Summary Review Questions Chapter 2: The Ecology of Evolution 2.1 Introduction 2.2 Evolution by natural selection 2.3 Evolution within species 2.3.1 Geographical variation within species 2.3.2 Variation within a species with man-made selection pressures 2.3.3 Adaptive peaks and specialized abysses 2.4 The ecology of speciation 2.4.1 What do we mean by a "species"? 2.4.2 Islands and speciation 2.5 The effects of climate change on the evolution and distribution of species 2.6 The effects of continental drift on the ecology of evolution 2.7 Interpreting the results of evolution: convergent and parallel evolution Summary Review Questions Chapter 3: Physical Conditions and the Availability of Resources 3.1 Introduction 3.2 Environmental conditions 3.2.1 What do we mean by "harsh," "benign," and "extreme"? 3.2.2 Effects of conditions 3.2.3 Conditions as stimuli 3.2.4 The effects of conditions on interactions between organisms 3.2.5 Responses by sedentary organisms 3.2.6 Animal responses to environmental temperature 3.2.7 Microorganisms in extreme environments 3.3 Plant resources 3.3.1 Solar radiation 3.3.2 Water 3.3.3 Mineral nutrients 3.3.4 Carbon dioxide 3.4 Animals and their resources 3.4.1 Nutritional needs and provisions 3.4.2 Defense 3.5 The effect of intraspecific competition for resources 3.6 Conditions, resources, and the ecological niche Summary Review Questions Chapter 4: Conditions, Resources and the World's Communities 4.1 Introduction 4.2 Geographical patterns at large and small scales 4.2.1 Large-scale climatic patterns 4.2.2 Small-scale patterns in conditions and resources 4.2.3 Patterns in conditions and resources in aquatic environments 4.3 Temporal patterns in conditions and resources - succession 4.4 The terrestrial biomes 4.4.1 Describing and classifying biomes 4.4.2 Tropical rain forest 4.4.3 Savanna 4.4.4 Temperate grasslands 4.4.5 Desert 4.4.6 Temperate forest 4.4.7 Northern coniferous forest (taiga) grading into tundra 4.5 Aquatic environments 4.5.1 Stream ecology 4.5.2 Lake ecology 4.5.3 The oceans 4.5.4 Coasts 4.5.5 Estuaries Summary Review Questions Chapter 5: Birth, Death and Movement 5.1 Introduction 5.1.1 What is an individual? 5.1.2 Counting individuals, births, and deaths 5.2 Life Cycles 5.2.1 Life cycles and reproduction 5.2.2 Annual life cycles 5.2.3 Longer life cycles 5.3 Monitoring birth and death: life tables and fecundity schedules (Part conents)

Journal ArticleDOI
TL;DR: In this paper, the Century ecosystem model was used to explore the role of soil texture in belowground C storage, nutrient pool sizes, and fluxes in highly weathered soils in an Amazonian forest ecosystem.
Abstract: Soil texture plays a key role in belowground C storage in forest ecosystems and strongly influences nutrient availability and retention, particularly in highly weathered soils. We used field data and the Century ecosystem model to explore the role of soil texture in belowground C storage, nutrient pool sizes, and N fluxes in highly weathered soils in an Amazonian forest ecosystem. Our field results showed that sandy soils stored approximately 113 Mg C ha-1 to a 1-m depth versus 101 Mg C ha-1 in clay soils. Coarse root C represented a large and significant ecosystem C pool, amounting to 62% and 48% of the surface soil C pool on sands and clays, respectively, and 34% and 22% of the soil C pool on sands and clays to 1-m depth. The quantity of labile soil P, the soil C:N ratio, and live and dead fine root biomass in the 0–10-cm soil depth decreased along a gradient from sands to clays, whereas the opposite trend was observed for total P, mineral N, potential N mineralization, and denitrification enzyme activity. The Century model was able to predict the observed trends in surface soil C and N in loams and sands but underestimated C and N pools in the sands by approximately 45%. The model predicted that total belowground C (0–20 cm depth) in sands would be approximately half that of the clays, in contrast to the 89% we measured. This discrepancy is likely to be due to an underestimation of the role of belowground C allocation with low litter quality in sands, as well as an overestimation of the role of physical C protection by clays in this ecosystem. Changes in P and water availability had little effect on model outputs, whereas adding N greatly increased soil organic matter pools and productivity, illustrating the need for further integration of model structure and tropical forest biogeochemical cycling.

Journal ArticleDOI
TL;DR: In this article, a map of the vegetation of the Hood River region of the Central Canadian Arctic derived from a supervised classification of Landsat Thematic Mapper (TM) satellite imagery is presented.
Abstract: Understanding mesoscale patterns of ecosystem properties is important if we are to effectively monitor ecosystem change due to land use and climate change Remote sensing provides the best tool for looking at large areas of the earth's surface to analyze, map, and monitor ecosystem patterns and processes Patterns of vegetation and variation in biodiversity are important ecosystem properties, with strong relationships to important ecosystem functions Species richness is the most widely used measure of biodiversity, and mapping patterns of species richness within a landscape can provide a basis for future monitoring and an ecological basis for land management and conservation decisions This study presents (1) a map of the vegetation of the Hood River region of the Central Canadian Arctic derived from a supervised classification of Landsat Thematic Mapper (TM) satellite imagery, (2) estimations and maps of regional variation in plant species richness, and (3) a comparison of three species richness estimat

Journal ArticleDOI
TL;DR: In this article, the authors compared ecosystem processes and properties east and west of the Continental Divide, and found that even slight increases in atmospheric deposition lead to measurable changes in ecosystem properties.
Abstract: We asked whether 3–5 kg N y−1 atmospheric N deposition was sufficient to have influenced natural, otherwise undisturbed, terrestrial and aquatic ecosystems of the Colorado Front Range by comparing ecosystem processes and properties east and west of the Continental Divide. The eastern side receives elevated N deposition from urban, agricultural, and industrial sources, compared with 1–2 kg N y−1 on the western side. Foliage of east side old-growth Englemann spruce forests have significantly lower C:N and lignin:N ratios and greater N:Mg and N:P ratios. Soil % N is higher, and C:N ratios lower in the east side stands, and potential net N mineralization rates are greater. Lake NO3 concentrations are significantly higher in eastern lakes than western lakes. Two east side lakes studied paleolimnologically revealed rapid changes in diatom community composition and increased biovolumes and cell concentrations. The diatom flora is now representative of increased disturbance or eutrophication. Sediment nitrogen isotopic ratios have become progressively lighter over the past 50 years, coincident with the change in algal flora, possibly from an influx of isotopically light N volatilized from agricultural fields and feedlots. Seventy-five percent of the increased east side soil N pool can be accounted for by increased N deposition commensurate with human settlement. Nitrogen emissions from fixed, mobile, and agricultural sources have increased dramatically since approximately 1950 to the east of the Colorado Front Range, as they have in many parts of the world. Our findings indicate even slight increases in atmospheric deposition lead to measurable changes in ecosystem properties.

Journal ArticleDOI
TL;DR: In this article, the authors show that changes in climate (precipitation and temperature) can have a significant effect on the quality of surface waters, and management strategies in a warmer climate will therefore be needed that are based on local ecological thresholds rather than annual median condition.
Abstract: Data from long-term ecosystem monitoring and research stations in North America and results of simulations made with interpretive models indicate that changes in climate (precipitation and temperature) can have a significant effect on the quality of surface waters. Changes in water quality during storms, snowmelt, and periods of elevated air temperature or drought can cause conditions that exceed thresholds of ecosystem tolerance and, thus, lead to water-quality degradation. If warming and changes in available moisture occur, water-quality changes will likely first occur during episodes of climate-induced stress, and in ecosystems where the factors controlling water quality are sensitive to climate variability. Continued climate stress would increase the frequency with which ecosystem thresholds are exceeded and thus lead to chronic water-quality changes. Management strategies in a warmer climate will therefore be needed that are based on local ecological thresholds rather than annual median condition. Changes in land use alter biological, physical, and chemical processes in watersheds and thus significantly alter the quality of adjacent surface waters; these direct human-caused changes complicate the interpretation of water-quality changes resulting from changes in climate, and can be both mitigated and exacerbated by climate change. A rigorous strategy for integrated, long-term monitoring of the ecological and human factors that control water quality is necessary to differentiate between actual and perceived climate effects, and to track the effectiveness of our environmental policies.

Journal ArticleDOI
TL;DR: Grasshoppers may speed up nitrogen cycling by changing the abundance and decomposition rate of plant litter, which increases total plant abundance, and whether grasshoppers enhance plant abundance depends on how much they consume.
Abstract: Ecologists hold two views about the role of herbivory in ecosystem dynamics. First, from a food web perspective in population/community ecology, consumption by herbivores reduces plant abundance. Second, from a nutrient cycling perspective in ecosystem ecology, herbivory sometimes slows down cycling, which decreases plant abundance, but at other times speeds up cycling, which possibly increases plant abundance. The nutrient cycling perspective on herbivory has been experimentally addressed more thoroughly in aquatic systems than in terrestrial systems. We experimentally examined how grasshoppers influence nutrient cycling and, thereby, plant abundance and plant species composition over a period of 5 years. We examined how grasshoppers influence nutrient (nitrogen) cycling (i) by their excrement, (ii) by changing the abundance of and the decomposition rate of plant litter, and (iii) by both. Grasshoppers may speed up nitrogen cycling by changing the abundance and decomposition rate of plant litter, which increases total plant abundance (up to 32.9 g/m(2) or 18%), especially, the abundance of plants that are better competitors when nitrogen is more available. However, whether grasshoppers enhance plant abundance depends on how much they consume. Consequently, ecosystems and food web perspectives are not mutually exclusive. Finally, under some conditions, grasshoppers may decrease nutrient cycling and plant abundance.